Process for the manufacture of methylamine



Patented Aug. 20, 1935 PROCESS non THE MANUFACTURE OF METHYLAMINE HenryDreyfus, London, England No Drawing. Application February 11, 1933,

Serial No. 656,366 In Great Britain March 9,

13 Claims.

This invention relates to the production of methylamine.

According to the invention methylamine is produced by treatment ofsolutions or suspensions and particularly aqueous solutions orsuspensions of cyanides with hydrogen (or gas containing and preferablyrich in the same) in the presence of a hydrogenating catalyst. Asexamples of hydrogenating catalysts particularly suitable for employmentin the process may be mentioned those consisting of or comprising themetals nickel, copper, zinc, iron, cobalt, tin and silver which may bepresent in anyconvenient form, for example as a colloidal dispersion orother suspension of the finely divided metals.

Alkali metal cyanides e. g. sodium cyanide, potassium cyanide, potassiumferro-cyanide and earth alkali cyanides are very suitable for employmentin the process of the invention and so likewise are the cyanides ofhydrogenating metals, i. e. metals, such as those specified above, whichare capable of acting as hydrogenating catalysts. When cyanides ofhydrogenating metals are employed the use of additional hydrogenatingcatalysts may, if desired, be dispensed with. Preferably, when cyanidesof hydrogenating metals are treated by the process of the presentinvention, they are used at least partly in the form oftheir doublecompounds with alkali metal cyanides.

The cyanide solutions or suspensions employed may be acid, neutral oralkaline in reaction as desired. When acid solutions are employed theamount of acid present may be equal to or less than that equivalent tothe cyanide employed or, if desired, sufficient acid may also be presentto combine with all or part of the methylamine subsequently formed.Preferably, however, neutral or alkaline solutions or suspensions of thecyanides are employed. I The reaction, the chief product of which ismono-methylamine, may be caused to take place as desired at normal,super-atmospheric or reduced pressure.

In carrying out the process of the invention elevated temperatures andespecially temperatures approaching the boiling point, under thepressure obtaining, of the medium in' which the cyanides are dissolvedor suspended are preferably employed. For instance, when treatingaqueous solutions or suspensions temperatures of between '70 and 95 C.are especially suitable when using pressures at or about ordinaryatmospheric pressure, whilst temperatures of between '70 and 230 C., andespecially between 150 and 200 C., are advantageous when high pressures,e. g. up to 20 atmospheres, are employed.

The hydrogen may be caused to react in any convenient manner, forinstance it may be passed in a stream through the cyanide solution orsussimple admixture of the gases or by pension which is maintained at asuitable tempcrature; in this manner (providing the solution does notcontain free acid) the methylamine I'ormed can be distilled or. carriedaway by the gas stream. Further, hydrogen may be forced into thesolution or suspension, contained in a pressure vessel maintained at asuitable temperature, until no more hydrogen is absorbed.

If desired, cyanide used up in the reaction vessel may be replenishedbycontinuous or intermittent addition of hydrogen cyanide. Thus hydrogencyanide maybe passed in together with the hydrogen.

When hydrogen cyanide is used inadmixture with hydrogen, preferablymixtures containing a considerable proportion of hydrogen, for exampleabout to 16 or more volumes of hydrogen -to one volume of hydrogencyanide, are employed. The mixture of hydrogen and hydrogen cyanide,when employedjmay of course be obtained in any desired manner, forexample by I passing hydrogen in a regulated stream over or throughliquid hydrogen cyanide.

In cases where the gases are passed through the solution in a stream thegases, after treatment to remove the methylamine, may be recirculatedthrough the apparatus.

The reaction vessel containing the cyanide solution or suspension may,when the process is carj ried out as acontinuous operation, be providedwith means whereby water may be added to re place that removed byevaporation during the Methylamine produced by the process can berecovered or separated in any convenient way.

the gas stream for instance by condensation and/or by absorption bywater and/or acid.

Methylamine contained or remaining in the solution or suspensionemployed can be recovered in any convenient manner, e. g. bydistillation with or without passage of inert gases through thesolutions or suspensions, alkali being added first in cases where theprocess is performed in an acid medium (e. g. in the presence ofhydrochloric acid or the like).

The following examples illustrate the invention whichis not, however,limited thereto.

Example 1 A slight excess of sodium carbonate is added to a solution ofnickel sulphate containing finely divided pumice in suspension; Theproduct is filtered and the residue, after being washed, is driedgandreduced in a current 01 hydrogen at -Qawc- The catalyst thus produced issuspended ina 30% solution of potassium cyanide contained in anautoclave fitted with stirrers, the autoclave isclosed and heated to175-180? C. and hydrogen is pumped in to a pressure of about 15atmospheres.

When theabsorption of hydrogen has practically ceased the hydrogensupply is stopped and the autoclave iscooled to 90 -95 0. and opened.the gases and vapours leaving the autoclave being passed'through a watercooled condenser provided wi-tha receiver and the unco'ndens'ed gasesscrubbed with dilute hydrochloric acid to recover "escaping methylamine.I autoclave are-distilled until free from methyl- The contents: of, the

amine; a V Example? Freshly precipitated-nickel cyanide is suspend- V edin five times its weight of water and .a quantity, equal to 11 times theweight of nickel cyani'de used, ofa saturated (517159 0.) solution ofpotassium cyanideis added i The Well stirred mixture is then treated asin Exam I What I claimiandqdesire to secure by Letters 1. Process forthe manufacture of methylamine which coniprises subjecting a solution orsuspension of a metal cyanide to treatment with 'hl i n ent e Q ahY r sna a ys said solution or suspension containing -QN ions s n a dionsgesenbc V P c j e the man fac e O in bh aw ine which comprisessubiejcting an aqueoussoluzt n or us en ion eras alka i met ra de totreatment with hydrogen presence of a hydrofina ins yst, said sa u on'or us en o containing CN ions as the only acid ions present.

. 3-. Pr c s f h m nu ac ur of m dl amwh h. emprises sub e t ng a ueousqlu- Qrsus en on f n i. m l c ani e to t m n wi hydro i fmte c Qt a dgenating metal selected from the group consisting o ni el c p en. Zinc,i a in mi a d silver,

, sai qlut qn, br us ens n, cqata n ne ,C I io a in enl ac d was eseit.-.

4- P oces for e manuia r i m thyi m i e-w ich q mpri e ub ct an aq ssome time sr n of a cyanide of a hydrogenatins metal, he We mewaitress;sit-i sut qn q suseens n Qn J ne+CN ons s as d sns presen 7 c Is i c c 5- ErQces m: h m n-ufiae r Qt vmsth l mmewi k; om rises subjectn a r o ut sus ns on at a, yanid ifi a r r en m a se ct d item h 2- qnsist ns of. nickel 9p- .per zinc, i on o a t n a d. s lve to re tmWith,.. .ydr ea a sq u e 9r s n Qn 0 sta nin C'N io s s the n y ac d 1 Pnt- I '6 Process for the manufacture of methyla m- J ine which comprisessubjecting an aqueous solution or suspension of an alkali metalcyanideand a cyanide of a hydrogenating metal to treatment with hydrogen inpresence of a free hydrogenating metal, said solutionor suspensioncontaining CN ions as the only acid ions present.

7. Process for the manufacture of methylamine which comprises subjectingan aqueous solution or suspension of an alakli rnetal cyanideand acyanide of a hydrogfil ating metal to treatment with hydrogen inpresenceof a free hydrogenating metal, said hydrogenating metal beingselectedfrom the group consisting of nickel, copper,

zinc, iron, cobalt, tin and silver, and said solution or suspensioncontaining -CN ions'as the only acid ions present.

8. Process for themanufacture of methylam- 'ine which comprisessubjecting an aqueous solution or suspension of an alkali metal cyanideand a cyanide of a hydrogenating metal to treatment With hydrogen inpresence of a hydrogenatingmetal selected iroin the' group consisting ofnickel, copper, zinc, iron, cobalt,.tin and'silver in finely dividedform, said solution or suspcnsi'oncontaining CN ions as the onlyacidions present; a a i s 9. Process for the manufacture ofmethylamine whichcomp-rises subjecting an aqueous-solution or suspension of a metalcyanide to treatment with hydrogen at temperatures of 70-95 C.

and in presence of a hydrogenating catalyst, said solution or suspensioncontaining --CN ions as the only acid ionspresent. c

10. Process for the'manufacture of methylamine which comprisessubjecting an aqueous solution or suspension of ametal cyanide to treat-'ment-at temepratures of- 150-200" C. with hydrogen under such pressurethat the solutiomor suspension is near its boiling'point andin presenceof a'hydrogenati-ng catalyst,- said solution or suspensioncontaining CNions as the only acid ions present. .c 1-1. Process for the manufactureof methlyania ine which comprises subjecting an aqueous solution-orsuspension of an alkali metal cyanide to treatment at temperatures of70-230 C. with hy- 40 drogen under such pressure that the solution orsuspension is near its boiling point and in pres ence of a hydrogenatingmetal selected from the group consisting of nickel, copper, zinc, iron,co-

balt, tin and silver, said solutionor suspension suspension containingCN ions as the onlyacid ions present.

13. Process for the'manufactu-re of methyla mine which comprisessubjecting anaqueous"so1u-' tion or suspension of an alkali metalcyanide-"and a cyanide ofa hyd'rogenating metal to treatment attemperatures of Hi-230 G; with hydrogen under such pressure thatthesolution or suspension is near its boiling point in presence of fafinely di vided' hydrogenating metal, said hydrogenating 565 metal beingselected from the group consisting of nickeLcopper, zinc, iron, cobalt,tin and silver, and said solution or suspensioncontaining ionsas theonly acid ions present. p

HENRY DREYF-US;

